The recombinant herpes zoster vaccine is effective in older adults regardless of a patient’s immunocompromised status, based on data from more than 3 million adults aged 65 years or older. The recommended second dose further increased effectiveness against shingles.

The CDC recommends shingles vaccination as a two-dose series of injections given 2-6 months apart.

However, vaccine uptake for one or two doses remains relatively low. Data from the CDC show that 18.1% of eligible adults aged 50 years or older in the US received two or more doses of the vaccine in 2022, while 25.6% received one or more doses.

Clinicians “should ensure that patients receive both recommended doses, as our study demonstrates the superior effectiveness of two doses compared to one,” said Nadja A. Vielot, PhD, epidemiologist in the Department of Family Medicine at the University of North Carolina School of Medicine in Chapel Hill, North Carolina. “This information could be helpful to patients who experienced adverse events after the first dose and are hesitant to receive the second,” she said.

The shingles vaccine has been available for nearly 10 years, and Vielot and her colleagues set out to assess effectiveness and safety over longer periods than were initially studied.

In the study published in the Annals of Internal Medicine, the researchers conducted analyses to measure the effectiveness of one or more shingles vaccine doses compared with none, and a second analysis measured the effectiveness of two doses compared with one dose. The study population included 3.45 million adults enrolled in Medicare fee-for-service between 2007 and 2019.

The primary outcome was contracting herpes zoster; secondary outcomes included ophthalmicus and postherpetic neuralgia.

In the first analysis, the 1-year vaccine effectiveness (VE) was 56.1% against any of the outcomes. The effectiveness of the vaccine was similar across age groups ranging from 65 to 80 years. A subgroup analysis of individuals who had previously received a live zoster vaccine showed VE of 51.8% compared with 57.7% among those who had not received a previous live zoster vaccine.

In the second analysis, the relative VE of two recombinant zoster vaccine (RZV) doses against any of the three outcomes was 67.9% compared with 56.1% for a single dose of RZV. The median time between doses was approximately 4.5 months. A sensitivity analysis accounting for receipt of the second dose within 2-6 months after the first dose yielded effectiveness of 68.1%.

The relative 1-year effectiveness of a second dose was 67.4% and 80.7% for the ophthalmicus and postherpetic neuralgia, respectively.

In subgroup analyses, VE with at least one dose was lower in individuals aged 85 years or older (44%) than in the overall study population (56.1%) and similar in immunocompromised and immunocompetent individuals (54.2% and 56.5%, respectively). Notably, VE of one dose was approximately 20% in Black individuals compared with approximately 55% in non-Black individuals. However, low representation of Black and Hispanic individuals likely resulted in imprecise estimates for these groups, Vielot said.

Previous studies have shown a low background incidence of shingles among Black individuals, Vielot said.

“We do not believe that vaccine recommendations should take race or ethnicity into consideration,” Vielot added.

Vielot said she and her colleagues are running a similar analysis using private insurance claims to assess the safety of the shingles vaccine relative to shingles infection.

Clinical Considerations

Shingles can be a particularly debilitating and painful condition, and the current study was important to assess the vaccine’s performance among adults older than 65 years, including those who are immunocompromised, said Shirin Mazumder, MD, infectious diseases specialist and associate professor at the University of Tennessee Health Science Center in Memphis, Tennessee.

Barriers to vaccination include problems with access, lack of insurance, and concerns about side effects, Mazumder told Medscape Medical News. Establishing reminder systems, improving convenience and accessibility, promoting vaccine programs that reduce financial burdens, and having open conversations with patients regarding any hesitancy are potential solutions to overcoming these barriers, she said.

“Research looking into factors contributing to disparities in vaccine effectiveness among different racial groups would also be useful given the findings in this study,” she said.

The study was supported by the National Center for Advancing Translational Science. The researchers and Mazumder reported having no financial conflicts to disclose.